The effect of fuel composition on swirling kerosene flames

摘要

In this work, the effect of kerosene composition on bluff-body, swirl stabilised spray flames is investigated using flame visualisation techniques. Two kerosene types were investigated: A conventional Jet-A blend, referred to as A2, and an alternative Gevo ATJ kerosene, referred to as CI. Flame photographs, OH* chemiluminescence images, simultaneous OH planar laser induced fluorescence (PLIF) and Mie scattering, and fuel PLIF images all show differences in flame appearance and structure as A2-air and C1-air flames approach extinction. A2-air flames appear to produce more soot than C1-air flames, as expected noting the composition of A2 includes a large content of alkylben-zenes and cycloaromatics, typically associated with an increased sooting tendency in hydrocarbon fuels. A2 fuel drops also appear to fluoresce substantially more than C1 in the OH-PLIF filtering scheme, which is also likely due to the aromatic and ring structure content of the fuel. Additional differences between the kerosene flames include flame brush characteristics, regions above the bluff-body containing fuel liquid and vapour, and flame attachment behaviour. C1-air flames show signs of extinction, marked by the PDF of lift-off height from the base of the combustor, at lower bulk air velocities and higher equivalence ratios than A2-air flames. This indicates that, at the conditions studied here, C1-air flames may be more easily extinguished than A2-air flames. This observation is supported by lean blow-off data presented at a range of fuel flow rate conditions. These findings, particularly relating to lean blow-off, are particularly important to consider during the development of fuel flexible lean gas turbine combustors.